Thad Allen, former Commandant, Coast Guard

As head of the national response team for the BP Deepwater Horizon oil spill, Adm. Thad Allen was charged with the monumental task of directing 47,000 workers from multiple federal, state and local agencies to stop the hundreds of millions of gallons gushing into the Gulf Coast.

Allen was tapped to be National Incident Commander just three weeks before his retirement as the 23rd commandant of the Coast Guard. As head of the cleanup team, Allen became the government's go-to person, the liaison between private contractors and government, and the public face for the government response to the worst environmental disaster in U.S. history.

The biggest challenge was bringing "unity of effort" across the various departments and agencies, Allen said.

"Taking together the combined resources, capabilities and competences of the various departments and agencies and understanding their authorities and jurisdictions, and knitting it all together to create a whole of government response that doesn't disenfranchise anybody --that's an enormous effort," Allen said.

To do this, agencies must agree on the goals and make the "means and ends" transparent, he said.

With the extensive media coverage and the use of social media (including an app that tracked the oil spill), the public became an active participant in disseminating information about the response.

"Managing one of these crises sometimes takes on a semblance of a reality show," Allen said.

To the public, it may have seemed "strange that the entity that caused the problem will be part of the solution and recovery," he said.

"There were a lot of inferences about whether are not (BP was) doing the right thing, whether or not they were subordinating corporate goals to cleaning the environment," Allen said.

But the response team had to rely on BP's technology and expertise, as well as private contractors in the oil spill response, as part of the Oil Pollution Act of 1990. So the government role in the oil spill -- opposed to a natural disaster -- was more about oversight than actual implementation, Allen said.

The oil spill was also very different from a natural disaster response in that the federal government had "pre-eminence," not local or regional authorities, he said.

Working with government agencies means working in a political environment. The response, Allen said, was "as much as a political event as an operational event."

"The more senior you get, you're going to have to learn how to be effective without being political, and by political I mean partisan," Allen said. "And that's the key to working in Washington."

Allen leaves the response team with high praise from the Obama administration as he joins RAND as a senior fellow to work on homeland security, ocean policy and defense policy issues.